The present invention relates generally to vehicle hydraulic fluid management systems.
Modern motor vehicles are equipped with numerous fluid based systems, e.g., anti-lock brake systems, ride control systems, or traction control systems, that provide comfort and safety to drivers and passengers of these vehicles. Each of these systems require numerous hydraulic actuators that direct the flow of hydraulic fluid between the system components when necessary. For example, a typical anti-lock brake system can include several hydraulic actuators to control the fluid pressure in the individual components, e.g., a master cylinder, and a plurality of wheel cylinders.
The memory of an actuator control system includes numerous look-up tables which allow the control system to know what electric signals, e.g., current values, to apply to the actuators in order to yield specific actuation pressures. Typically, these look-up tables are generic tables that are not tailored to the individual actuators in the fluid system. These generic tables are created to account for worst-case part-to-part variances, manufacturing variances, and system variances. Thus, the tolerances of the values contained in the tables are relatively large and result in less than optimal performance of the actuators.
As recognized by the present invention, very expensive actuators can be used to decrease part-to-part variances, but the overall system tolerances remain larger than the tolerances that can be obtained by individually calibrating less expensive actuators to create customized look-up tables for each actuator.
The present invention has recognized the prior art drawbacks, and has provided the below-disclosed solutions to one or more of the prior art deficiencies.
A method for calibrating a hydraulic actuator includes applying a series of electrical signals to the actuator. For each applied electrical signal, the actuation pressure of the actuator is measured. Then, based on predetermined pressure values, unwanted signals are filtered out to create a customized look-up table for the actuator.
In a preferred embodiment, the customized look-up table is stored in a database. Preferably, multiple actuators are assembled to form a module assembly and the customized look-up table for each actuator is accessed. Based on the customized look-up tables, electrical signals are applied to each actuator and an actuation pressure is measured for each electrical signal. Based on the measured actuation pressures, the customized look-up tables are adjusted and then, the adjusted customized look-up tables are stored in a database. In a preferred embodiment, the electrical signals include a current sweep from a minimum value to a maximum value back to the minimum value. In another aspect of the present invention, the electrical signals include a voltage duty cycle sweep from a minimum value to a maximum value back to the minimum value.
In yet another aspect of the present invention, an actuator device test system includes a test stand. An actuator device is installed in the test stand. In this aspect of the present invention, the test stand includes a control circuit that includes logic means for creating a customized look-up table for the actuator device.
In still another aspect of the present invention, an actuator module assembly is calibrated. Initially, a customized look-up table is established for each hydraulic actuator in the actuator module assembly. Then, the actuators are assembled to form the module assembly. Thereafter, signals are applied to each actuator. Based on the responses of the actuators to the signals, an adjusted customized look-up table is established for each actuator.